Disposable safety syringe

ABSTRACT

A safety syringe  10  includes a generally tubular body  14  having a needle end  18  and plunger end  22,  needle  38  and retractable needle seat  30,  two-way valve  36,  plunger  42,  stopper  62,  piston  52,  and rear plunger seal  44.  During use, the plunger may be moved to create a vacuum in the plunger. The user then moves the plunger toward the needle end, pressurizing a vial, then pulls backward to a selected position corresponding to the desired volume of fluid to be withdrawn. At the conclusion of the injection stroke, the piston is disengaged from the plunger. The vacuum within the plunger retracts the needle safely into the tubular body.

FIELD OF THE INVENTION

[0001] The present invention relates generally to syringes and, moreparticularly, to syringes having retractable needles. The inventionspecifically relates to a disposable, retractable needle syringe whichutilizes created vacuum to automatically retract the needle into thesyringe body and thereby prevent the healthcare practitioner fromgetting stuck by the needle.

BACKGROUND OF THE INVENTION

[0002] Hypodermic syringes provide an effective, reliable, andinexpensive way to inject a measured quantity of medicine below theskin. Syringes typically have exposed needles, however, and the ease bywhich a needle may pierce the skin creates a hazard that the healthcareworker may accidentally be stuck with a needle. The resulting injurycould be as simple as a minor skin laceration, or as deadly as aninfection from a virus in the patient's blood.

[0003] Because syringes are routinely used worldwide, occasionalinjuries are inevitable when using conventional syringes. Healthcarepractitioners are exposed to this danger in routine medical practice.Diabetics, people with arthritis, and others who self-administer dailyinjections are at risk, as are members of their household. Afterdisposal, conventional syringes may continue to pose a risk tosanitation workers and anyone else who comes in contact with landfillsand waste management processes. Some syringes will undoubtedly bedisposed of or handled improperly prior to disposal, increasing thechance of injury. Despite their utility, conventional syringes thusclearly pose a danger to healthcare practitioners.

[0004] The prior art discloses methods of reducing or eliminating thedangers associated with exposed syringe needles. U.S. Pat. No. 4,908,022describes a disposable safety syringe having a retractable needle. U.S.Pat. No. 5,885,257 describes a syringe having a spring-loaded,automatically retractable needle. U.S. Pat. No. 5,000,736 describes asyringe having a sealed tubular plunger from which air has beenevacuated and a needle releasably attached to the distal end. After thepatient is injected, the plunger seal is ruptured and the differentialpressure between the vacuum and ambient air causes the needle to retractsafely within the syringe body. U.S. Pat. No. 6,193,695 describes asyringe having a sealed portion between the plunger and end cap. As theplunger is pulled away from the needle to fill the syringe, a one-wayvalve in the sealed portion opens, allowing air to be expelled from thesealed portion. During injection, the plunger is moved toward the needleto expel its contents, the valve closes, and the pressure in the sealedportion decreases. At the end of its stroke, the plunger captures theneedle, and the relatively low pressure in the sealed portion causes theplunger and needle to retract into the syringe body. Other patents ofinterest include U.S. Pat. Nos. 4,425,120; 4,643,200; 4,675,005;4,692,156; 4,747,830; 4,816,022; and 4,790,822.

[0005] Although the prior art has addressed many of the safety problemsrelated to conventional hypodermic syringes, numerous shortcomingsremain relating to the cost of manufacturing and the safe use ofsyringes with retractable needles (safety syringes). Some safetysyringes require storage of potential energy, which may be unreliable.For example, sealed vacuum chambers are prone to leakage when thesyringe is stored for an extended period. Other safety syringes may haveneedles which retract a limited distance, with the retracted needleremaining dangerously close to the syringe body opening. Some syringesare shipped and stored with plungers fully extended, increasing theirpackaged size with a corresponding decrease in the efficiency ofshipping and storage. Syringes which utilize springs are costly, andrequire additional seals to prevent contamination of the fluid drawninto the body of the syringe. Further shortcomings exist in the priorart with regard to manufacturing cost, ease of use, and reliability ofsafety syringes. A reliable syringe which automatically retracts theneedle into the syringe body is sought which overcomes the disadvantagesof the prior art.

[0006] The present invention surpasses the prior art, offering animproved safety syringe that is both reliable and economical. Theretractable-needle or safety syringe of the present invention isrelatively simple and convenient to operate.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to a safety syringe thatretracts its needle into a syringe body to prevent the healthcarepractitioner from accidentally getting stuck by the exposed needle. Theretractable needle protects various people, including healthcareworkers, their patients, and sanitation workers involved with disposalof medical waste. The invention may prevent or reduce injuries rangingfrom minor skin lacerations to serious contamination by medications,germs, or viruses. The syringe preferably is a disposable, single-usedevice, and may be available in various sizes and shapes. A syringeaccording to this invention may also be used in non-medicalapplications, such as chemical handling processes.

[0008] It is an object of the present invention to provide an improvedvacuum operated, retractable-needle (safety) syringe. A preferredembodiment includes a selectively retractable needle assembly comprisinga needle seat for supporting a needle, and a generally tubular body thatserves as a reservoir for injectable or withdrawn fluids. A hollowplunger moves axially within the generally tubular body, and extendsfrom the plunger end of the body for engagement by the health carepractitioner. A stopper or other seal between the plunger and tubularbody prevents air from passing into or out of the tubular body throughthe plunger end. As explained below, the hollow plunger is axially movedto draw fluid into the syringe, expel fluid from the syringe into thepatient, and create a vacuum within the tubular body, which results in avacuum in the hollow plunger due to a one-way valve, preferably createdby the stopper and ports in the wall of the hollow plunger. A two-wayvalve, a removable plug, or other controllable plug regulates the flowof liquid and air flowing into and out of the needle end of the tubularbody during use. A piston moves axially within the internal chamber inthe plunger, and a seat/piston latch selectively engages the needle seatand the piston to withdraw the needle into the hollow plunger due to thecreated vacuum. Movement of the plunger to the full injection positionengages the seat/piston latch, releases the needle seat, and releasesthe piston from the plunger. The syringe may be distributed and storedin a relatively compact packaged configuration, with the plungersubstantially retracted into the tubular body.

[0009] To use the syringe, the healthcare practitioner may first pullthe plunger from its packaged configuration within the syringe bodytoward the plunger end of the body. Since the needle end of the body isclosed off by a plug, the created vacuum in the body receives air frominside the plunger. The stopper thus also serves as a one way valve toallow air flow from within the plunger to the interior of the body tocreate a vacuum in the plunger, while preventing reverse flow.

[0010] To fill the syringe body, the practitioner may first insert theneedle into a vial or other fluid source and move the plunger axiallytoward the needle end of the tubular body, thereby pressurizing thevial. The practitioner may then pull the plunger axially to apredetermined measurement toward the plunger end of the body to drawfluid into the tubular body. The practitioner may then aspirate thesyringe in a conventional manner, eliminating air and any excess liquid.To inject the patient, the practitioner inserts the needle under theskin and forces the plunger toward the needle end of the body to expelthe liquid. At the end of the plunger injection stroke, the plungerreaches the full injection position, the seat/piston latch engages theneedle seat and the piston, and the piston and needle seat are released,so that the piston and retractable needle assembly now move togetherwith respect to the tubular body. The vacuum within the plungerautomatically pulls the piston toward the rear end of the plunger,retracting the needle safely within the plunger and the syringe body.

[0011] It is an object of this invention to provide an improved safetysyringe. The safety syringe may operate more reliably and consistentlythan other safety syringes. Because the vacuum in the plunger may becreated during the initial movement of the plunger, there is no need foran energy source within the syringe to retract the needle which maydegrade or fail prior to use. A related object of the invention is toprovide an improved safety syringe which uses a vacuum within thegenerally tubular body of the syringe created by movement of the plungerto withdraw the needle seat and the attached needle into the generallytubular body.

[0012] Another object of the invention is to provide an improved methodof using a syringe of the type with a needle seat sealingly engagedwithin the tubular body for supporting a needle, with the needle seatbeing releasably retained on the tubular body in an initial position. Apractitioner may apply a first axial force to a needle end plugged bodyto move the plunger to a displaced position, creating a vacuum withinthe tubular body, which becomes the vacuum within the hollow plunger dueto a one-way valve. The practitioner then inserts the needle into theliquid source and withdraws a selected volume of liquid into the tubularbody. After aspirating the air, the needle is inserted into a fluidrepository, such as a patient, and a second axial force on the plungeris used to discharge liquid from the needle. At the end of the injectionstroke, a seat/piston latch connects the needle seat with the piston,the needle seat disengages from the tubular body, and the pistondisengages from the plunger so that the released piston and connectedneedle seat and needle are moved as an assembly to the retractedposition within the plunger and also within the tubular body.

[0013] It is a feature of the invention that a one-way valve is providedfor allowing fluid flow from the interior chamber in the plunger to thethroughbore of the generally tubular body, thereby allowing a vacuumwithin the tubular body to create a vacuum within the plunger, whilepreventing flow in a reverse direction. In a preferred embodiment, theone-way valve comprises one or more through ports in the plunger, with astopper normally closing off flow through the ports and opening theports to create the partial vacuum within the plunger interior chamber.

[0014] A further feature of the invention is that movement of theplunger to the full injection position causes the piston to engage theneedle seat and release a piston/plunger latch to release the pistonfrom the plunger may include a male and female connector. A shoulder onthe piston may pass axially out of a retaining groove in the plunger,thereby releasing the piston from the plunger.

[0015] It is also a feature of the invention that the needle seat isretained in its initial position by engagement with the generallytubular body, and that moving the plunger to the fully injected positionmay cause the plunger to radially expand a portion of the generallytubular body, thereby releasing the needle seat from the tubular body. Arelated feature of the invention is that a needle seat retainer, whichmay also serve as a seal between the needle seat and the tubular body,may be engaged by the plunger when in the full injection position tounseal the connection and release the needle seat from the tubular body.In either case, the plunger, when moved to the full injection position,disengages the seat retainer, thereby releasing the needle seat from thebody.

[0016] A further feature of the invention is the practitioner uses theimproved syringe in a manner very similar to operation of a conventionalsyringe. Graduations on the tubular body increase from the needle endtoward the plunger end so that the practitioner withdraws the selectedamount of fluid into the syringe, then inserts that fluid into therepository, which causes the needle seat and needle to automaticallywithdraw within the tubular body.

[0017] A feature of the invention is that a simple plug at the needleend of the syringe body may be used as a controllable plug to preventair from entering the tubular body when the plunger is moved to create avacuum, and may thereafter be removed to allow fluid communication fromoutside to within the syringe body. The plug may be provided in the formof a cap which covers or blocks off the needle end of the syringe priorto use, such that the healthcare practitioner creates the vacuum bymoving the plunger while a syringe body needle end is plugged by the capor plug.

[0018] A significant advantage of the present invention is that thesyringe may be manufactured at a relatively low cost, and accordinglythe syringe preferably is a disposable single-use device.

[0019] Another significant advantage of the present invention is thatthe safety syringe may be easily and safely operated by thepractitioner.

[0020] These and further objects, features, and advantages of thepresent invention will become apparent from the following detaileddescription, wherein reference is made to the figures in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 illustrates in cross-section one embodiment of the safetysyringe according to the present invention in an initial, packagedconfiguration.

[0022]FIG. 2 is an enlarged cross-sectional view of a portion of thesyringe shown in FIG. 1.

[0023]FIG. 3 shows the plunger pulled to create a vacuum in the tubularbody.

[0024]FIG. 4 illustrates in greater detail the ports in the plunger, sothat the stopper opens these ports when a partial vacuum exists in thetubular body.

[0025]FIG. 5 shows the syringe ready for use with vacuum created and theneedle installed on the syringe body.

[0026]FIG. 6 shows the needle end of the syringe in an ampule,preferably pressuring the ampule.

[0027]FIG. 7 shows the syringe after the plunger has been moved to aselected, displaced position.

[0028]FIG. 8 shows the syringe aspirated for insertion into a patient.

[0029]FIG. 9 shows the injection complete, releasing the needle seat andthe piston.

[0030]FIG. 10 shows in greater detail the piston and needle seatconnection.

[0031]FIG. 11 shows the syringe with its needle in a fully retractedposition after use.

[0032]FIG. 12 is an exploded view of an embodiment without a needlemounted on the syringe.

[0033]FIG. 13 shows a plug or cap closing off a needle secured to theneedle end of the tubular body, with the plunger pulled back toinitially create vacuum.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0034]FIG. 1 shows a syringe 10 in an initial packaged configuration forshipment and storage, with greater detail of the needle seat and pistonshown in FIG. 2. A generally tubular body 14, which may house medicineor other liquid during use of the syringe 10, has a needle end 18, anopposing plunger end 22, and a cylindrical throughbore 26 with a centralaxis 27. The tubular body 14 is preferably plastic, but may compriseother non-porous or leak proof materials.

[0035] As shown in FIG. 2, a needle seat 30 is received within thethroughbore 26 and at least partially within the reduced diameterportion 29 at the needle end 18 of the tubular body 14. The needle seat30 may be axially and sealingly attached to the tubular body 14, held inan initial retained position by a seat retainer 33, which may be agenerally annular bead on either the needle seat 30 or on the tubularbody 14, which engages a similarly configured groove on the other of theneedle seat or tubular body. The tubular body sealingly receives theneedle seat when in the initial retained position, with the seal beingformed by sealing engagement of the components themselves, or by aseparate seal between the needle seat and the tubular body. The needleseat 30 is configured for release from the body 14, as discussed below.

[0036] The needle seat 30 supports a needle 38 (see FIG. 5) which maypierce a layer of skin to transport medicine or other liquidsubdermally. The needle seat 30 as shown in FIG. 2 may be configured forattachment to a conventional hub 31 as shown in FIG. 5 by a quarter-turnspiral-lock conventionally used with syringes, with the hub 31supporting the needle 38 thereon. The needle seat 30 is selectivelymoveable from the initial retained position (see FIG. 1) to a needleretracted position (see FIG. 11), wherein the attached needle 38 is atleast substantially internal to the plunger, and also within the tubularbody 14. The seat retainer 33 is shown in the initial retainer positionin FIG. 2, in the released position in FIG. 10, and in the retractedposition in FIG. 11. In a preferred embodiment, the seat/body retainer33 as shown in FIG. 6 may comprise a generally circumferential bead onthe seat 14 cooperating with an annular groove on the body.Alternatively, the bead could be pivoted on the body, the groove on theneedle seat.

[0037] Referring again to FIG. 1, the plunger 42 may be used to expelthe contents of the syringe 10 toward the needle end 18 and out throughthe needle 38. The plunger 42 has a needle seat end 46 positioned withinthe tubular body 14 and an opposed plate end 50 extending from thetubular body 14, with the plunger 42 being axially moveable relative tothe tubular body 14. An annular rear stop 44 is preferably provided forpreventing the plunger 42 from moving out of the tubular body 14. Theplunger has a push/pull plate 51 on the plate end 50. The plungerinterior is sealed by the plate 51, and cooperates with the piston 52 toseal an interior chamber 43 in the plunger sized for sealing engagementwith the piston 52 to withdraw the piston and the needle into thechamber 43, as discussed further below. The piston 52 is axiallyretained initially on the plunger 42 by a piston/plunger retainer 54, asshown in FIG. 2. The body 14 may include radially opposing finger tabs53, as shown in FIG. 1.

[0038] The initial configuration of the syringe as shown in FIG. 1 isrelatively compact, with the plunger 42 substantially within the tubularbody 14. The stopper 62 seals between the body 14 and the plunger 42,and is positioned near the needle end 18 of the body 14.

[0039] To initiate the filling process, the plunger 42 is first movedinto a retracted position (see FIG. 3). Air in the annulus between thebody 14 and the plunger passes by the rear stop 44, and out the body 14.A simple plug or cap as shown in FIG. 13 prevents air from entering thetubular body through the needle end during this movement of the plunger,thereby creating a vacuum within the body between the needle seat andthe plunger. In one embodiment, the needle is secured in place on thesyringe body, and the cap closes off the needle to prevent air fromentering the needle. In another embodiment, the cap may close off theneedle end of a syringe without a needle mounted thereon, and the cap orplug may then seal directly to the syringe. After the vacuum is createdwithin the syringe, the needle may then be secured to the syringe.

[0040] The stopper 62 is axially secured to the plunger 42 by connector63, and a forward portion 64 of the stopper as shown in FIG. 4 normallycovers a plurality of cicumferentially spaced ports 66 in the plunger. Acreated vacuum in the tubular body and the ambient pressure within theplunger 42 lifts the portion 64 of the stopper out of sealing engagementwith the exterior surface of the plunger surrounding the ports 66,thereby allowing air within the plunger 42 to pass into the tubular body14, so that a partial vacuum exists both within the tubular body 14 andwithin the plunger 42. A particular feature of the present invention isthe use of a stopper 62 which both forms a seal between the plunger andthe tubular body and which also acts as a one way valve to allow air toescape from within the plunger through the port 66, while preventingflow from within the tubular body to the interior of the plunger.

[0041] The needle 38, which may then be installed on a syringe or maypreviously have been secured to the body 14 by the needle seat 30, maythen be inserted into the vial or other fluid source 68, then theplunger 42 moved forward to pressurize the vial, as shown in FIG. 6. Theplunger 42 may then be moved back toward the plunger end 22 of thetubular body 14 to a liquid withdrawn position, as shown in FIG. 7,drawing a desired volume of liquid from the fluid source 68 into thesyringe 10. The stopper 62 is closed since pressure in the body 14 isgreater than pressure within the plunger 42. Air may then be aspiratedfrom within the tubular body 14 through the needle 38. The syringe 10and its contents are now ready for the injection process.

[0042] After the needle 38 has been inserted below the skin of apatient, the plunger 42 is forced axially toward the needle end 18, asshown in FIG. 8, and the fluid is forced by the stopper 62 out throughthe needle 38 and into the patient. At the end of the injection stroke,the piston/seat latch 54 axially connects the piston and the needle seat30, thereby capturing the needle seat 30, as shown in FIG. 10. At theend of the injection stroke, the needle end 82 of the plunger 42 asshown in FIG. 10 has radially expanded the needle end 18 of the body 14due to the camming action of surface 84 on the plunger and the matingsurface 86 on the body, until the plunger engages the stop surface 88 onthe body, which is the complete or full injection position. Theexpansion of the needle end 18 of the tubular body thus releases theneedle seat 30 from the body. At the same time, i.e., at the fullinjection position, stop surface 53 on the piston 52 has engaged theface 31 of the needle seat 30, as shown in FIG. 10, but forward motionof the needle seat is prevented by the stop surface 90 on the bodyengaging the needle seat. Accordingly, the piston/plunger retainer 92,which may consist of annular bead or shoulder on the piston 52 whichresides within an expanded diameter groove 94 on the plunger 42, isforced rearward with respect to the plunger a slight amount to releasethe piston/plunger retainer. In this full injection position, asubstantial vacuum exists in the plunger relative to the atmosphericpressure or slight positive pressure due to the injection stroke in thetubular body 14 on the opposing side of the piston 52. When thepractitioner releases the plunger 42 at the end of its injection stroke,the released piston 52, the disengaged needle seat 30 and attachedneedle 38 are retracted into a retracted position within the tubularbody 14 (see FIG. 11). While the piston is retracted within the plunger,a guide 51 on the piston may be used to retain the piston in axialalignment within the throughbore 43 in the plunger.

[0043] Preferably the syringe according to the present invention is adisposable single-use device. Plunger 42 may include a plurality ofcircumferentially spaced ribs 98 for maintaining proper alignment of theplunger with respect to the body during axial movement or stroking ofthe plunger. The stopper 62 is secured axially to the plunger, andpreferably forms the seal between the body and the plunger and acts asthe valve member closing off the ports in the plunger when pressuresurrounding the plunger is greater than pressure within the plunger. Apreferred piston/seat latch mechanism according to the present inventionmay include a male member on a piston and a female member on the seat.The male member could alternatively be provided in the seat and thefemale member on the plunger. The needle may be shipped separately fromthe syringe, and the needle then attached to the needle seat in aconventional manner. In other embodiments, the needle and needle seatcould be formed as a single unit, and the syringe shipped with theneedle extending from the tubular body.

[0044] Various types of rear stops may be used for preventing theplunger from coming completely out of the tubular body. Various types ofplungers and pistons may be used for reliably sealing with the tubularbody and the plunger during axial movement of the plunger and thepiston. Other types of retainers maybe used for initially retaining theseat 30 in the needle end of the tubular body, and thereafter yieldingor releasing the seat once engaged by the plunger to withdraw the needleseat and needle into the tubular body.

[0045] The method of the present invention will be readily understood tothose skilled in the art in view of the above discussion. The syringewhen used has the needle seat sealingly engaging the generally tubularbody and retained in an initial retained position. The stopper isprovided within the throughbore of a tubular body, and a plunger extendsat least partially within the throughbore of the tubular body. A createdvacuum in the tubular body 14 when the plunger is moved away from theplugged needle end of the tubular body results in a vacuum within thetubular body 14, which may be substantially equal to the vacuum in theplunger 42 due to the release of air from the plunger by the one-wayaction of the stopper 62. Once a vacuum is created within the plunger,the plug may be removed from the needle end of the body 14. In oneoption, the needle 38 and the hub 31 may then be threaded onto theneedle seat. The vacuum within the tubular body 14 is intentionallylost, but the vacuum in the plunger 42 is maintained.

[0046] A needle may then be inserted into the liquid source, butpreferably is inserted into the liquid source prior to applying axialforce to the plunger to pressurize the liquid source (typically a vial)with air. A selected volume of liquid from the liquid source is thenwithdrawn into the tubular body between the needle seat and the stopperwhile moving the stopper from a selected displaced position to a fluiddrawn position. The practitioner conventionally pulls the plunger backto draw fluid into the syringe, as shown in FIG. 7. The tubular body 14may thus include graduations 96 on an outer surface of the tubular bodywhich increase from the needle end to the plunger end, allowing thehealthcare practitioner to withdraw a selected volume of liquid into thethroughbore 26 of tubular body 14. After removing the needle from theliquid source and aspirating the air from the syringe, the needle may beinserted into a fluid repository, such as the patient. Thereafter, asecond axial force is applied by the practitioner to the plunger to movethe plunger toward the needle end of the tubular body to dischargeliquid from the tubular body. At the end of the injection stroke, theseat/piston latch is engaged to connect the needle seat with the piston,the piston 52 is released from the plunger 42, and the needle seat 30 isreleased from the body 14. The second force is then relaxed, allowingthe piston 52 and connected needle seat 30 and needle 38 to move fromthe initial retained position to the needle seat retracted position.

[0047] As discussed above, a removable plug may serve to prevent entryof air into the syringe from the needle end of the tubular body. FIG. 13discloses a cap or plug 96 which may seal over the needle secured to thesyringe during manufacture, as discussed above, so that the userinitially pulls the plunger to create the vacuum as shown in FIG. 13, sothat the cap 96 thereafter may be removed from the needle and thesyringe and be discarded. In a preferred embodiment, the needle issecurely mounted on the syringe body at this time, although in alternateembodiments the syringe and plug could be provided separately from theneedle.

[0048] The cap as discussed above is a preferred way to plug or seal theneedle end of the tubular body until the vacuum has been created withinthe plunger. Various types of plugs may be used for this purpose. Forexample, a female plug may be used to slide over a male member on theneedle end of the plunger body. An alternative plug may act as a malemember for closing off the entry port in the needle end of the tubularbody. As a further alternative, a pressure responsive flow valve or apressure release valve may be used for closing off the entry port in theneedle end of the tubular body.

[0049] As discussed above, the stopper acts as both a seal between theplunger and the syringe body and cooperates with ports in the plunger toact as a one-way valve. In a less desired alternative, the stopper maybe used as only a seal, and another mechanism used as a one-way valve. Aseparate one-way valve might be provided, for example, within apassageway in the piston, allowing opening of the valve to obtain thevacuum within the plunger, but then automatically closing the valve onceair enters the needle end of the syringe body and pressure in thesyringe is greater than pressure within the plunger. As discussed above,the stopper is preferably axially secured to and moveable with theplunger, although limited axial movement between the stopper and theplunger would be permissible in some applications. Various types andconfigurations of pistons may be used for sealing with the interior ofthe plunger to withdraw the piston and the needle into the plunger.

[0050] According to the preferred embodiment discussed above, theplunger is moved to the full injection position, thereby initiallyengaging the piston with the needle seat. At substantially the sametime, the seat/piston latch axially connects the needle seat with apiston, the needle seat is released from engagement with the tubularbody, and the piston is released for moving with the captured needle andthe needle seat to a retracted position within the plunger and withinthe tubular body. These three actions preferably occur simultaneously,or may occur in any sequence desired by the syringe manufacturer. Theprimary point is that once the plunger is moved to the full injectionposition, the force supplied by the user to the plunger may be released,and automatically reactions occur which cause the needle to be safelyretracted within the syringe body.

[0051] A particular feature of the present invention is that the syringehas a relatively low cost, and the needle is reliably drawn into thetubular body after use. The syringe according to the present inventionis particularly well suited for use when injecting a small quantity offluid, e.g., less than 10 cc, and in some applications the tubular bodymay hold less than a maximum of about 5 cc.

[0052] In addition to medical applications, the syringe may be used inother nonmedical applications. For example, if using the syringe forchemical extraction and disposal, rather than injection into a patient,the syringe 10 may be used to inject fluid into a different type offluid receptacle, such as an open flask or other chemical handlingmedia. The needle 38 may be designed accordingly to accommodate thedesired process. For example, whereas a human patient may require use ofa narrow, sharp needle, chemical extraction and disposal may require alarger needle to extract larger volumes of chemical fluids, or fluidswith a higher viscosity.

[0053] It may be appreciated that changes to the details of theillustrated embodiments and systems disclosed are possible withoutdeparting from the spirit of the invention. While preferred andalternative embodiments of the present invention have been described indetail, it is apparent that further modifications and adaptations of thepreferred and alternative embodiments may occur to those skilled in theart. However, it is to be expressly understood that such modificationsand adaptations are within the spirit and scope of the presentinvention, as set forth in the following claims.

What is claimed is:
 1. A syringe for retracting a needle supported on aneedle seat, comprising: a generally tubular body having a needle endand an opposing plunger end, the tubular body having an internalthroughbore extending between the needle end and the opposing plungerend, the tubular body sealing receiving the needle seat therein; aseat/body retainer adjacent the needle end of the tubular body forinitially attaching the needle seat to the generally tubular body, theneedle seat being selectively moveable within the tubular body from aninitial retained position to a needle seat retracted position; a plungerhaving an interior chamber therein and a needle seat end positionedwithin the internal throughbore of the generally tubular body, theplunger being moveable within the throughbore of the tubular body; astopper for sealed engagement between the generally tubular body and theplunger; a piston selectively moveable between an initial retainedposition adjacent the needle seat end of the plunger and a pistonretracted position within the plunger; a one-way valve allowing flowfrom the interior chamber in the plunger to the throughbore in thegenerally tubular body while preventing fluid flow from the throughborein the generally tubular body to the interior chamber in the plunger; aseat/piston latch for selective engagement of the needle seat with thepiston; and a controllable plug selectively preventing fluid fromentering the tubular body through the needle end when in a closedposition.
 2. A syringe as defined in claim 1, wherein the one-way valvecomprises one or more through ports in the plunger, and the stopper ismoveable relative to the one or more ports between a closed position forclosing off flow through the ports and an open position for opening theports to create a partial vacuum within the plunger interior chamber. 3.A syringe as defined in claim 2, wherein the stopper automatically movesradially outward to the open position in response to reduced pressure inthe tubular body throughbore compared to pressure in the interiorchamber in the plunger.
 4. A syringe as defined in claim 1, wherein thepiston is selectively move retained in the initial retained position bya piston/plunger retainer, and the piston engages the needle seat todisengage the piston/plunger retainer and release the piston to moveaway from the needle seat end of the plunger.
 5. A syringe as defined inclaim 1, wherein: the seat/piston latch includes one of a male connectorand a female connector secured to the plunger and the other of the maleconnector and the female connector secured to the piston.
 6. The syringeas defined in claim 1, further comprising: graduations on the tubularbody increasing from the needle end toward the plunger end.
 7. A syringeas defined in claim 1, further comprising: a plate secured to a plateend of the plunger for applying an axial force to the plunger.
 8. Asyringe as defined in claim 1, wherein the stopper is axially secured toand moveable with the plunger.
 9. A syringe as defined in claim 1,further comprising: a stop secured to the tubular body for preventingthe plunger from coming fully out of the tubular body.
 10. A syringe asdefined in claim 1, wherein the controllable plug is a manually removedplug.
 11. A syringe as defined in claim 10, wherein the removable plugseals a needle supported on the tubular body end, and is manuallyremoved subsequent to creating a vacuum with the plunger.
 12. A syringeas defined in claim 10, wherein the removable plug seals the needle endof the tubular body and is manually removed subsequent to creating avacuum within the plunger.
 13. A syringe as defined in claim 1, whereinmovement of the plunger to an injection position expands a portion of agenerally tubular body to release the seat/body retainer and the needleseat from the tubular body.
 14. A syringe as defined in claim 1, whereina seal between the needle seat and the tubular body retains the needleseat in the initial retained position, and movement of the plunger to aninjection position moves the seal such that the needle seat is releasedfrom the generally tubular body.
 15. A syringe for retracting a needlesupported on a needle seat, comprising: a generally tubular body havinga needle end and an opposing plunger end, the tubular body having aninternal throughbore extending between the needle end and the opposingplunger end, the tubular body sealing receiving the needle seat therein;a seat/body retainer adjacent the needle end of the tubular body forinitially attaching the needle seat to the generally tubular body, theneedle seat being selectively moveable within the tubular body from aninitial retained position to a needle seat retracted position; a plungerhaving an interior chamber therein and a needle seat end positionedwithin the internal throughbore of the generally tubular body, theplunger being sealed to the tubular body and moveable within thethroughbore of the tubular body; a piston selectively moveable betweenan initial retained position adjacent the needle seat end of the plungerand a piston retracted position within the plunger the piston beingselectively retained in the initial retained position by apiston/plunger retainer, and the piston engages the needle seat todisengage the piston/plunger retainer and release the piston to moveaway from the needle seat end of the plunger; a one-way valve allowingflow from the interior chamber in the plunger to the throughbore in thegenerally tubular body while preventing fluid flow from the throughborein the generally tubular body to the interior chamber in the plunger; aseat/piston latch for selective engagement of the needle seat with thepiston; and a controllable plug selectively preventing fluid fromentering the tubular body through the needle end when in a closedposition.
 16. A syringe is defined in claim 15, wherein thepiston/plunger retainer includes a shoulder on one of the piston and theplunger for positioning within a groove on the other of the piston andthe plunger when the piston is in the initial retained position.
 17. Asyringe as defined in claim 15, wherein the one-way valve comprises oneor more through ports in the plunger, and a stopper which seals betweenthe body and the plunger is moveable relative to the one or more portsbetween a closed position for closing off flow through the ports and anopen position for opening the ports to create a partial vacuum withinthe plunger interior chamber.
 18. A syringe as defined in claim 15,wherein: the seat/piston latch includes one of a male connector and afemale connector secured to the plunger and the other of the maleconnector and the female connector secured to the piston.
 19. A syringeas defined in claim 15, wherein the controllable plug seals a needlesupported on the tubular body and is manually removed subsequent tocreating a vacuum within the plunger.
 20. A syringe as defined in claim15, wherein movement of the plunger to an injection position expands aportion of a generally tubular body to release the seat/body retainerand the needle seat from the tubular body.
 21. A syringe as defined inclaim 15, wherein a seal between the needle seat and the tubular bodyretains the needle seat in the initial retained position, and movementof the plunger to an injection position moves the seal such that theneedle seat is released from the generally tubular body.
 22. A syringefor retracting a needle supported on a needle seat, comprising: agenerally tubular body having a needle end and an opposing plunger end,the tubular body having an internal throughbore extending between theneedle end and the opposing plunger end, the tubular body sealingreceiving the needle seat therein; a seat/body retainer adjacent theneedle end of the tubular body for initially attaching the needle seatto the generally tubular body, the needle seat being selectivelymoveable within the tubular body from an initial retained position to aneedle seat retracted position; a plunger having an interior chambertherein and a needle seat end positioned within the internal throughboreof the generally tubular body, the plunger being sealed to the tubularbody and moveable within the throughbore of the tubular body; a pistonselectively moveable between an initial retained position adjacent tothe needle seat end of the plunger and a piston retracted positionwithin the plunger; a one-way valve allowing flow from the interiorchamber in the plunger to the throughbore in the generally tubular bodywhile preventing fluid flow from the throughbore in the generallytubular body to the interior chamber in the plunger; a seat/piston latchincluding one of a male connector and a female connector secured to theplunger and the other of the male connector and the female connectorsecured to the piston for selective engagement of the needle seat withthe piston; and a controllable plug selectively preventing fluid fromentering the tubular body through the needle end when in a closedposition.
 23. A syringe as defined in claim 22, wherein the one-wayvalve comprises one or more through ports in the plunger, and a stopperwhich seals between the body and the plunger is moveable relative to theone or more ports between a closed position for closing off flow throughthe ports and an open position for opening the ports to create a partialvacuum within the plunger interior chamber.
 24. A syringe as defined inclaim 22, further comprising: graduations on the tubular body increasingfrom the needle end toward the plunger end; and a plate secured to aplate end of the plunger for applying an axial force to the plunger. 25.A syringe as defined in claim 22, wherein movement of the plunger to aninjection position expands a portion of a generally tubular body torelease the seat/body retainer and the needle seat from the tubularbody.
 26. A syringe as defined in claim 22, wherein a seal between theneedle seat and the tubular body retains the needle seat in the initialretained position, and movement of the plunger to an injection positionmoves the seal such that the needle seat is released from the generallytubular body.
 27. A method of using a syringe with a needle seatsupporting a needle retractable in a generally tubular body having aninternal throughbore extending between a needle end and an opposingplunger end, the method comprising: sealingly engaging the needle seatwith the generally tubular body, the needle seat being selectivelymovable from an initial retained position to a needle seat retractedposition; releasably retaining the needle seat in the initial retainedposition; axially securing a stopper to a plunger within the throughboreof the tubular body; positioning the plunger at least partially withinthe throughbore of the tubular body, the plunger including an internalchamber therein; positioning a piston within the plunger moveable froman initial position in the needle end of the plunger to a retractedposition within the internal chamber in the plunger; providing a one-wayvalve between the internal chamber in the plunger and the throughbore ofthe generally tubular body; plugging the needle seat end of the tubularbody; applying a first axial force to move the plunger from an initialposition in the opposing plunger end of the tubular body to a selecteddisplaced position, thereby creating a vacuum within the tubular bodybetween needle end of the tubular body and the stopper and opening theone-way valve to obtain a vacuum within the plunger; removing the plugin the needle seat end of the tubular body; inserting a needle into aliquid source; withdrawing a selected volume of liquid from the liquidsource through the needle and into the tubular body between the needleseat and the stopper while moving the plunger to a fluid drawn position;thereafter inserting the needle into a fluid repository; thereafterapplying a second axial force to the plunger to move the stopper towardthe needle end of the tubular body while discharging liquid from withinthe tubular body; engaging a seat/piston latch to axially connect theneedle seat with the piston; and relaxing the second force to disengagethe needle seat from the generally tubular body and move the piston andthe connected needle seat from the initial retained position to theneedle seat retracted position.
 28. A method as defined in claim 27,wherein the needle is inserted into the liquid source before moving theplunger to the displaced position, thereby pressurizing the liquidsource while the plunger moves to the displaced position.
 29. A methodas defined in claim 27, wherein providing a one way valve includesproviding one or more ports in the plunger, the stopper covering the oneor more ports to close the valve when pressure within the body isgreater than pressure within the plunger.
 30. A method as defined inclaim 27, wherein movement of the plunger to a full injection positionreleases the piston from a retained position on the plunger.
 31. Amethod as defined in claim 27, further comprising: engaging the pistonwith the needle seat to release the piston from the plunger to move thepiston axially away from the needle end of the plunger.
 32. A method asdefined in claim 27, wherein a wrapper encloses the tubular body to plugthe needle end of the tubular body, and moving the plunger to create thevacuum opens the wrapper to unplug the needle end of the tubular body.33. A method as defined in claim 27, further comprising: providinggraduations on the tubular body increasing from the needle end towardthe plunger end.
 34. A method as defined in claim 27, furthercomprising: moving the plunger to an injection position such that theplunger expands a portion of the generally tubular body to release theneedle seat.
 35. A method as defined in claim 27, further comprising:moving the plunger to an injection position such that the plunger movesa seal between the seat and the tubular body to release the needle seat.36. A method of using a syringe with a needle seat supporting a needleretractable in a generally tubular body having an internal throughboreextending between a needle end and an opposing plunger end, the methodcomprising: sealingly engaging the needle seat with the generallytubular body, the needle seat being selectively movable from an initialretained position to a needle seat retracted position; releasablyretaining the needle seat in the initial retained position; axiallysecuring a stopper to a plunger within the throughbore of the tubularbody; positioning the plunger at least partially within the throughboreof the tubular body, the plunger including an internal chamber therein;positioning a piston within the plunger moveable from an initialposition in the needle end of the plunger to a retracted position withinthe internal chamber in the plunger, wherein the piston is selectivelyretained in the initial retained position by a piston/plunger retainer,and the piston engages the needle seat to disengage the piston/plungerretainer and release the piston to move away from the needle seat end ofthe plunger; providing a one-way valve between the internal chamber inthe plunger and the throughbore of the generally tubular body; pluggingthe needle seat end of the tubular body; applying a first axial force tomove the plunger from an initial position in the opposing plunger end ofthe tubular body to a selected displaced position, thereby creating avacuum within the tubular body between needle end of the tubular bodyand the stopper and opening the one-way valve to obtain a vacuum withinthe plunger; removing the plug in the needle seat end of the tubularbody; inserting a needle into a liquid source; withdrawing a selectedvolume of liquid from the liquid source through the needle and into thetubular body between the needle seat and the stopper while moving theplunger to a fluid drawn position; thereafter inserting the needle intoa fluid repository; thereafter applying a second axial force to theplunger to move the stopper toward the needle end of the tubular bodywhile discharging liquid from within the tubular body; engaging aseat/piston latch to axially connect the needle seat with the piston;and relaxing the second force to disengage the needle seat from thegenerally tubular body and move the piston and the connected needle seatfrom the initial retained position to the needle seat retractedposition.
 37. A method as defined in claim 36, wherein the needle isinserted into the liquid source before moving the plunger to thedisplaced position, thereby pressurizing the liquid source while theplunger moves to the displaced position.
 38. A method as defined inclaim 36, wherein providing a one way valve includes providing one ormore ports in the plunger, the stopper covering the one or more ports toclose the valve when pressure within the body is greater than pressurewithin the plunger.
 39. A method as defined in claim 36, furthercomprising: providing graduations on the tubular body increasing fromthe needle end toward the plunger end.
 40. A method as defined in claim36, further comprising: moving the plunger to an injection position suchthat the plunger expands a portion of the generally tubular body torelease the needle seat.
 41. A method as defined in claim 36, whereinplugging the needle seat end of the tubular includes supporting a needleon the tubular body and plugging the needle with a plug, and removingthe plug in the needle seat end of the tubular body includes removingthe plug from the needle.
 42. A method of using a syringe with a needleseat supporting a needle retractable in a generally tubular body havingan internal throughbore extending between a needle end and an opposingplunger end, the method comprising: sealingly engaging the needle seatwith the generally tubular body, the needle seat being selectivelymovable from an initial retained position to a needle seat retractedposition; releasably retaining the needle seat in the initial retainedposition; axially securing a stopper to a plunger within the throughboreof the tubular body; positioning the plunger at least partially withinthe throughbore of the tubular body, the plunger including an internalchamber therein; positioning a piston within the plunger moveable froman initial position in the needle end of the plunger to a retractedposition within the internal chamber in the plunger; providing a one-wayvalve between the internal chamber in the plunger and the throughbore ofthe generally tubular body; plugging the needle seat end of the tubularbody; applying a first axial force to move the plunger from an initialposition in the opposing plunger end of the tubular body to a selecteddisplaced position, thereby creating a vacuum within the tubular bodybetween needle end of the tubular body and the stopper and opening theone-way valve to obtain a vacuum within the plunger; removing the plugin the needle seat end of the tubular body, thereby closing the one-wayvalve; inserting a needle into a liquid source; withdrawing a selectedvolume of liquid from the liquid source through the needle and into thetubular body between the needle seat and the stopper while moving theplunger to a fluid drawn position; thereafter inserting the needle intoa fluid repository; thereafter applying a second axial force to theplunger to move the stopper toward the needle end of the tubular bodywhile discharging liquid from within the tubular body; engaging a malemember on one of the piston and the needle seat with a female member onthe other of the piston and the needle seat to axially connect theneedle seat with the piston; and relaxing the second force to disengagethe needle seat from the generally tubular body and automatically movethe piston and the connected needle seat from the initial retainedposition to the needle seat retracted position.
 43. A method as definedin claim 42, wherein the needle is inserted into the liquid sourcebefore moving the plunger to the displaced position, therebypressurizing the liquid source while the plunger moves to the displacedposition.
 44. A method as defined in claim 42, wherein plugging theneedle seat end of the tubular includes supporting a needle on thetubular body and plugging the needle with a plug, and removing the plugin the needle seat end of the tubular body includes removing the plugfrom the needle.
 45. A method as defined in claim 42, wherein movementof the plunger to a full injection position releases the piston from theretained position on the plunger.
 46. A method as defined in claim 42,wherein providing a one way valve includes providing one or more portsin the plunger, the stopper covering the one or more ports to close thevalve when pressure within the body is greater than pressure within theplunger.
 47. A method as defined in claim 42, further comprising:providing graduations on the tubular body increasing from the needle endtoward the plunger end.
 48. A method as defined in claim 42, furthercomprising: moving the plunger to an injection position such that theplunger expands a portion of the generally tubular body to release theneedle seat.
 49. A method as defined in claim 42, further comprising:moving the plunger to an injection piston such that the plunger moves aseal between the seat and the tubular body to release the needle seat.50. A method as defined in claim 42, further comprising: engaging thepiston with the needle seat to release the piston from the plunger tomove the piston axially away from the needle end of the plunger.